


so lower your sights (but raise your aim)

by oryx



Category: Kamen Rider Build
Genre: Age Difference, Desk Sex, M/M, Praise Kink, Unhealthy Relationships
Language: English
Status: Completed
Published: 2018-02-17
Updated: 2018-02-17
Packaged: 2019-03-20 09:26:21
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,474
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13714782
Author URL: https://archiveofourown.org/users/oryx/pseuds/oryx
Summary: Sento gets more than he bargained for in the week leading up to the proxy battle.





	so lower your sights (but raise your aim)

**Author's Note:**

> it's a good day to write the dubious garbage that apparently has to be written by me

  
It’s the third day of this. Of desperately trying to master Hokuto and Seito’s bottles before –  
   
His grip tightens around the hilt of the Drill Crusher. He watches Stark’s movements with singular focus, his mind feeling frazzled but for this, like a section of shortcircuited wire still live with a few errant sparks. When Stark lifts the Steam Blade and lunges, Sento blocks the blow and reaches for the Whale and Jet bottles almost without thinking, like a mechanical reflex, sliding them into the driver and letting the new Best Match take hold. The blast of water from Whale/Jet forces Stark back, slamming him into the pillar behind him and sending him sinking down to the ground, and in an instant Sento moves to level the Drill Crusher directly at heart.  
   
And there he stops, breath coming quick and hot all around him. The tip of the Drill Crusher wavers as he presses it against Stark’s chestplate.  
   
Stark tilts his head to the side, visor glinting in the late afternoon light.  
   
“Well?” he says. “Are you going to do it or not?”  
   
Sento swallows hard. He could. He could do it right now, and some part of all this would end, simply and easily. One less puppeteer pulling the strings of this war. He’s already a killer. What’s another tally, really? This time it would be for good reason, too.  
   
And yet his hands are shaking. The anxious tension in his chest is wound so tight he feels fit to break.  
   
A moment later he tosses his weapon aside, the metal clattering against the pavement as his legs give out beneath him (whether from relief or sheer tiredness he can’t say). His knees hit the ground hard but he barely registers the pain.  
   
“Ah, well,” Stark sighs. “Not quite there yet, are we?” He reaches out to take the bottles from the Build Driver, his hand lingering there along Sento’s waistline a moment longer than it needs to before sliding them free, Build’s armor falling away. “But that’s alright. I’m not much in the mood to die today anyhow. And you’ve made good progress, you know. I’m proud of you.”  
   
Sento stares down at the cracked cement and can feel a shiver prickling along the back of his neck. “I don’t want to hear that from you,” he says, the detached chilliness he was going for hardly coming through.  
   
“No?” Isurugi cancels his own transformation as well, the mist receding to reveal a look of thoughtful contemplation. “I’d say you’re being a little dishonest, aren’t you? I mean. There’s a reason you came to me looking for validation. And there’s a reason you always pick up the phone when I call.”  
   
Sento’s mouth feels dry. “That’s only logic,” he hears himself say. “You seem to be holding most of the cards here, after all.”  
   
Isurugi laughs, eyes crinkling around the corners, and Sento wonders how it’s possible, for that expression to be virtually indistinguishable from when he used to welcome him back after a battle.  
   
“True enough,” he muses. “But that’s not the whole truth, is it? Really, what it comes down to is that… I made you. I gave you a name, an identity. The  _person_ ,” here there is a hint of wry humor as he says that word, as if it were some obvious joke, “known as Kiryu Sento never would have existed without me. And creations always crave the acceptance of the one who created them. That’s just how it works, Sento-kun.”  
   
He lifts a hand to palm his neck, gentle at first, until his fingers curl around his nape and dig into his skin as he tugs him forward, forcing him to meet his eyes. His smile is exactly as usual – cheerfully benign – and yet Sento feels caught, an animal that’s just stepped into a hunter’s trap.  
   
“And so when I say ‘I’m proud of you,’ there’s no shame in feeling a little happy about it. It’s a very natural response. I hope you know that.”  
   
Something seems to flip disconcertingly in the pit of Sento’s stomach. It takes more effort than it should to swat Isurugi’s hand away, hyper-conscious of the absence when his vice-like grip is gone, of the exact outline of his fingertips.  
   
Isurugi studies him for a long moment; claps him on the shoulder, jarringly good-natured, as he gets to his feet. “Well. That’s enough for today, I suppose. If I keep you much longer, they’re going to get suspicious, you know.” A pause. “What  _do_  you tell them, by the way? I’m dying to know.”  
   
Sento glares up at him. “I don’t tell them anything,” he says hotly. “But I. I  _implied_  before, that it was my girlfriend calling. So that might be what they assume.”  
   
Isurugi blinks. It’s the most genuine surprise Sento has ever seen on his face, and it lasts only a split second before his expression turns to one of delighted amusement. “You don’t say?” he murmurs. “I’m flattered, Sento-kun.”  
   
“Tell them your girlfriend sends her regards,” he says, turning away and lifting a hand in parting, and Sento watches him leave with a tight, anxious feeling in his throat that doesn’t fade at all when he turns the corner and vanishes from sight, like something in the air itself has shifted.  
   
  
   
  
   
The most unsettling part about emerging from the lab to find a very much alive Nariaki Utsumi brewing coffee behind the counter of the café, about hearing him say “Stark sent me to assist you in his stead” –  
   
The most unsettling part of it all is the disappointment.  
   
_So he doesn’t have time for me today_. That unwanted thought intrudes out of nowhere, splintering the door in his mind as it forces its way through, and visceral horror grips him as he considers it. Why would he think something like that? For what reason? In the minutes after, he feels displaced, off-set, like he’s been rattled hard enough to have shaken loose of himself, existing just a little to the left of his own body.  
   
With Utsumi, he goes through the motions on autopilot, coming back with a jolt only after he’s been broken from the Hazard Trigger’s influence.  
   
“It was quite the experiment,” Utsumi says, a small smile curving his mouth as he kneels there in the simulation, and Sento can only nod for lack of a better response. What does it say about him, he wonders, that he can do these things while barely present in his own mind? Could a human person truly be like this?  
   
He spends the next four hours tweaking his prototype for the killswitch until the blueprints bleed together into a mass of criss-crossed lines and data that he can see even when he closes his eyes.  
   
His focus is such that it takes him longer than it should to realize that the Build Phone is ringing, and he stares down at the caller ID with a weight seeming to sit between his ribs. He could prove him wrong right now, he thinks. Let it go to voicemail. Let him go ignored for once in his life.  
   
And yet his hand is already reaching out to press the Accept button. Maybe it was never an option at all.  
   
“So?” Isurugi says, without so much as a ‘hello.’ “Was Nariaki any use?”  
   
Sento takes a deep, steadying breath. “To an extent,” he says coolly. “He certainly has access to some powerful technology. Even if I’d known he was still alive, I never would’ve expected you to have him in your pocket.”  
   
“Having someone indebted to you goes a long way, you’ll find.” There is a beat of silence, in which Sento can picture his face perfectly: pensive and sly, sizing him up even over the phone. “Are you angry, Sento? Lonely because I skipped out on you today?”  
   
“You’re imagining things,” Sento fires back, too quick, his hand slowly curling into a white-knuckled fist against his thigh.  
   
Isurugi laughs, low and velvety soft. “No need to get defensive. We just talked about this yesterday, didn’t we? About being honest with yourself. And actually, I do have something I’d like to give you. I guess it could wait until tomorrow, but… Can you get away now?”  
   
Sento glances around at the empty lab dispassionately, a hollow feeling in his chest. “Well, no one’s here, so.”  
   
(“I think we should give him a little more space,” he’d overheard Sawa saying as she offered to bring Misora and Ryuga to her apartment for the night. Deep down, he knows what she really meant was this: “You don’t want to be around him right now, do you? That murderer.”  
   
He doesn’t blame them for it. If he could, he would leave himself behind, too.)  
   
“Really?” Isurugi sounds intrigued. “They’d leave you alone at a time like this?” He hums thoughtfully. “In that case I may as well come to you, then.”  
   
“That’s not – ” Sento is cut off by the click as Isurugi ends the call, and blinks down at the screen with trepidation tensing his shoulders.  
   
He’ll accept whatever it is and then tell him to leave, he says to himself, coaching. He won’t let him get under his skin. Not today.  
   
He’s standing at the whiteboard ten minutes later when he hears the eerily familiar sound of Isurugi’s footsteps descending down the staircase. He forces himself not to turn around.  
   
“This place is looking a bit of a mess, isn’t it?” Isurugi’s voice says. “You kids never were much for cleaning.”  
   
You took care of us too well, Sento thinks but does not say. We got complacent.  
   
“Did you come here just to nitpick?” he asks instead, filling in an integer for the equation he’s been puzzling over, then shaking his head and erasing it with the blade of his hand. “I thought you had something to give me.”  
   
“Ah, that’s right.” His voice is suddenly, alarmingly close, the lack of distance an almost tangible thing that Sento can feel at his back. “Well, to be totally honest, I just wanted to talk in person a bit. I got the results of the simulation from Nariaki right as I called you, actually. Very promising numbers. Maybe not enough to be able to control the Hazard Trigger in time for the proxy battle, which is a shame. But we are in a war, after all. Weapons are going to get broken here and there.”  
   
Sento freezes as he feels Isurugi’s fingers curl around his waist. As he feels him lean in close, his chest brushing Sento’s shoulderblades –  
   
The whiteboard marker drops to the floor with a clatter as he spins around, pressing himself back against the wall with his pulse hammering in his ears.  
   
“What do you think you’re doing?” he asks, trying and failing to keep his voice steady.  
   
The corner of Isurugi’s mouth quirks into a knowing smile. This time when he takes a step forward there is nowhere obvious for Sento to go, and he skirts sideways instead, circling around only to find himself trapped yet again, this time by his desk thumping against the backs of his thighs.  
   
“I’ve been thinking, lately,” Isurugi says, “that maybe some…  _positive_  reinforcement might be more effective. For a while now I’ve had to be hard on you, Sento. You understand, I’m sure. How valuable spite can be in terms of motivation. But things have changed.” He moves so that there are only sparse inches between them, tilting his head as he looks at Sento appraisingly. “You’re on the verge of mastering the Hazard Trigger already. Which is a much better progression than I could have hoped for. And so I’ve been thinking that maybe the two of us could go back to how things used to be, before all this unpleasantness.”  
   
He leans forward to place a hand on the desktop, like the bar of a prison, his other arm circling around him before he can react, fingers splayed against his back as he presses closer still, until Sento can feel the entire line of his body against his.  
   
“How you used to come home to me after defeating a Smash,” Isurugi says, directly into his ear, “and I would put an arm around your shoulders and say ‘good work, Sento-kun.’ ‘You’ve been doing so well, lately.’”  
   
Sento’s breath catches in his throat. He frees a hand and tries to push him away, tries to put space between them, but has no leverage to work with. In the end, he simply finds himself giving up, curling his fingers into the fabric of Isurugi’s jacket.  
   
“I just want you to know,” Isurugi says, “that I meant it genuinely. Then, and especially now. You’ve proven to be quite the success, you know. I really am so proud of you. Of everything you’ve accomplished. I’m glad I made you like I did.”  
   
Sento can’t help the quiet whimper that escapes his lips. He feels strange – lightheaded, dizzy, almost, Isurugi’s voice seeming to sink down beneath his skin and turn to liquid warmth. A warmth that travels downward and curls dark in the pit of his stomach, his cock stiffening against his thigh. Isurugi turns so that his mouth is all but brushing Sento’s jawline.  
   
“Do you want to hear more, Sento?” he asks.  
   
Sento’s voice is hoarse, his thoughts too full of static to feel any shame when he answers: “Yes.”  
   
Isurugi smiles against his skin. He pulls back just enough that he can look him in the eye, his expression as casually amiable as ever. “See? That wasn’t so hard, was it? Being upfront about your feelings. Now, let’s try it again. Is talking all you want me to do? Or do you want something else, too?”  
   
“I – ” Sento licks his lips. Some of his common sense seems to be returning to him, now, like a sudden douse of cold water to the face, and yet. He grimaces. “This is the worst. Don’t make me say it.”  
   
Isurugi laughs. “Ah, well. It was worth a shot. I’ll still give you what you want, though, since I’m in a good mood today.”  
   
He pulls back further, stepping away altogether, and Sento finds himself feeling bereft from the loss of contact. He’s fully hard now, straining against the taut denim in a way that is both obvious and discomfiting. Isurugi looks at him expectantly.  
   
“Well?” he says. “Get undressed.”  
   
“That’s – ” Sento’s scowl deepens. “Isn’t this all a little  _too_  cavalier? Even for you.”  
   
Amusement glints in Isurugi’s eyes. “Don’t take it personally,” he says. “These things tend to lose their mystique a bit once you’re older. You’ll understand someday.”  
   
Sento’s brow furrows as his hand strays haltingly to the zipper of his jeans. It hits him abruptly, then: how strange it is, that he’s never really given much thought to it. About who this person was before the Pandora Box changed him. About the friends, the significant others he must have had, years ago. A spouse, even. A loving marriage.  
   
But he supposes now isn’t the time to be contemplating it either, as he slides out of his jeans, and then – after a long moment of hesitation – his boxers. A deep flush burns the back of his neck as he sits there on the edge of the desk with the metal cold against his bare calves, his cock on display, precome already beading at the tip.  
   
Through it all, Isurugi’s placid smile never so much as falters.  
   
“There you go,” he says encouragingly, stepping forward again to slide in between Sento’s legs. His hand comes to rest against his inner thigh, broad and warm and firm, and Sento tenses up beneath the touch. His other hand cups his face, unnervingly gentle, and as he leans in to kiss him he murmurs: “Good boy.”  
   
Sento makes a choked sort of noise against his lips. He wonders how a few simple words from this person can drown out the noise that’s been in his head since that day. The meld of voices – Sawatari’s and Aikawa’s and his own – telling him that it’s over now. That he failed. He was supposed to save people, wasn’t he? Supposed to protect their lives. He isn’t good at all.  
   
And yet when Isurugi says it, it sounds true.  
   
It takes him a moment to realize that Isurugi’s palm is no longer there against his thigh; that he’s taking something from his pocket, which Sento is too lightheaded to consider the implications of until moments later when a slick finger is pressing against the curve of his ass. Instantly, he tenses up, pulse jumping.  
   
“This is what you wanted, isn’t it?” Isurugi asks, his mouth lingering at the corner of Sento’s own, and Sento forces his body to relax before nodding tersely.  
   
(He does want this. Doesn’t he? The static is turning his thoughts all fuzzy again.)  
   
He sucks in a breath as Isurugi’s finger enters him, and then another, pressing in and opening him up little by little. The strangeness of the sensation vanishes as soon as he crooks his finger just right, cock twitching as a thrill travels up the length of his spine. Sento finds himself reaching up unwittingly to hold on to Isurugi’s upper arms, a grip that must be vice-like, bruising, and yet Isurugi shows no sign of minding.  
   
“Please,” Sento says weakly. He isn’t entirely sure what he’s asking for, only that just this isn’t enough.  
   
He can feel Isurugi’s amusement without even looking at his face. “Well, since you’re asking so nicely.”  
   
Sento bites his lip as Isurugi’s lube-slick hand curls around him, stroking him slowly. As he slides another finger inside him, deeper than before, stretching him in a way that feels good and right. Every one of his nerves seems to be firing at once, thighs trembling, and Isurugi’s thumb swiping across the head of his cock is what sets him over the edge, coming with a shudder, his vision seeming to grey out for a moment as it moves through him like an electrical surge.  
   
He breathes heavily, overcome with tiredness in the empty silence left behind.  
   
His grip on Isurugi’s arms weakens and falls away, and Isurugi steps back, procuring a handkerchief from his jacket pocket and cleaning his hands, the picture of nonchalance. Sento sinks slowly down to the floor. His throat feels tight as he stares up at him.  
   
“You… Did you get anything out of that?” he asks, and hates how hurt his voice sounds. “Or are you just messing with me?”  
   
Isurugi arches an eyebrow. “Are you upset that I didn’t get off, too? My, my. What a considerate boy I’ve raised.” He crouches down so that they are at eye level. “Maybe next time, hm? When there’s a better occasion for it. Since I have a sneaking suspicion…”  
   
Here he trails off and lifts his gaze to the ceiling, and it’s only a few seconds later that Sento hears it: the distant jingle of the bell over the café’s front door. Footsteps, too, and voices – too quiet to make out at first, but then Ryuga, loud as usual:  
   
“He’s not a kid. He can deal with being alone for one night. And maybe it  _would_  be better for him.”  
   
“It’s obvious you wanted to come back, too,” Misora says, a frown in her voice. “The way you were standing by the window looking worried the entire time we were there – ”  
   
“I was not!”  
   
Sento blinks.  _They came back for me?_  he thinks, and that thought seems to get caught in the gears of his mind, repeating again and again.  
   
“So they do care about you,” Isurugi says with a smile. “Isn’t that heartwarming? You might want to think about getting dressed before they come down here, though. Bit of an awkward sight.”  
   
Sento looks back at him, meeting his eyes, a strange sort of ache wrapping itself around his heart.  
   
“I wish I understood you,” he says finally.  
   
Isurugi huffs out a quiet laugh, and it reminds Sento so much of late nights in the café, talking about the future with this person across from him, sipping at bad coffee that he always drank to the last drop anyhow.  
   
“I thought you were supposed to be a genius.”  
   
“I am,” he snaps. “I’m a physicist. Equations, formulas, the laws of motion… Those make sense. Nothing you do makes any sense at all.”  
   
Isurugi studies him for a moment before reaching out to grab him by the chin, a forceful grip, his thumb dragging across Sento’s bottom lip thoughtfully.  
   
“Maybe not yet,” he says.  
   
And at that he takes the Transteam Gun from within his jacket; pulls the trigger and is enveloped gradually by its mist, obscuring his features until only his smile is left, and then that too is hidden.


End file.
